Examinando por Autor "Castro-Severyn, Juan"

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    Biochemical, genomic and structural characteristics of the Acr3 pump in Exiguobacterium strains isolated from arsenic-rich Salar de Huasco sediments
    (Frontiers Media S.A., 2022-11) Castro-Severyn, Juan; Pardo-Esté, Coral; Araya-Durán, Ingrid; Gariazzo, Valentina; Cabezas, Carolina; Valdés, Jorge; Remonsellez, Francisco; Saavedra, Claudia P.
    Arsenic is a highly toxic metalloid of major concern for public safety. However, microorganisms have several resistance mechanisms, particularly the expression of arsenic pumps is a critical component for bacterial ability to expel it and decrease intracellular toxicity. In this study, we aimed to characterize the biochemical, structural, and genomic characteristics of the Acr3 pump among a group of Exiguobacterium strains isolated from different sites of the arsenic-rich Salar de Huasco (SH) ecosystem. We also determined whether the differences in As(III) resistance levels presented by the strains could be attributed to changes in the sequence or structure of this protein. In this context, we found that based on acr3 sequences the strains isolated from the SH grouped together phylogenetically, even though clustering based on gene sequence identity did not reflect the strain’s geographical origin. Furthermore, we determined the genetic context of the acr3 sequences and found that there are two versions of the organization of acr3 gene clusters, that do not reflect the strain’s origin nor arsenic resistance level. We also contribute to the knowledge regarding structure of the Acr3 protein and its possible implications on the functionality of the pump, finding that although important and conserved components of this family of proteins are present, there are several changes in the amino acidic sequences that may affect the interactions among amino acids in the 3D model, which in fact are evidenced as changes in the structure and residues contacts. Finally, we demonstrated through heterologous expression that the Exiguobacterium Acr3 pump does indeed improve the organisms As resistance level, as evidenced in the complemented E. coli strains. The understanding of arsenic detoxification processes in prokaryotes has vast biotechnological potential and it can also provide a lot of information to understand the processes of evolutionary adaptation. Copyright © 2022 Castro-Severyn, Pardo-Esté, Araya-Durán, Gariazzo, Cabezas, Valdés, Remonsellez and Saavedra.
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    Characterization of biofilm formation by Exiguobacterium strains in response to arsenic exposure
    (PubMed, 2023-12-12) Pavez, Valentina B.; Pacheco, Nicolás; Castro-Severyn, Juan; Pardo-Esté, Coral; Álvarez, Javiera; Zepeda, Phillippi; Krüger, Gabriel; Gallardo, Karem; Melo, Francisco; Vernal, Rolando; Aranda, Carlos; Remonsellez, Francisco; Saavedra, Claudia P.
    In this work, we characterized the composition, structure, and functional potential for biofilm formation of Exiguobacterium strains isolated from the Salar de Huasco in Chile in the presence of arsenic, an abundant metalloid in the Salar that exists in different oxidation states. Our results showed that the Exiguobacterium strains tested exhibit a significant capacity to form biofilms when exposed to arsenic, which would contribute to their resistance to the metalloid. The results highlight the importance of biofilm formation and the presence of specific resistance mechanisms in the ability of microorganisms to survive and thrive under adverse conditions.
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    Mobile genetic elements drive the multidrug resistance and spread of Salmonella serotypes along a poultry meat production line
    (Frontiers Media S.A., 2023-03) Krüger, Gabriel I.; Pardo-Esté, Coral; Zepeda, Phillippi; Olivares-Pacheco, Jorge; Galleguillos, Nicolas; Suarez, Marcia; Castro-Severyn, Juan; Alvarez-Thon, Luis; Tello, Mario; Valdes, Jorge H.; Saavedra, Claudia P.
    The presence of mobile genetic elements in Salmonella isolated from a chicken farm constitutes a potential risk for the appearance of emerging bacteria present in the food industry. These elements contribute to increased pathogenicity and antimicrobial resistance through genes that are related to the formation of biofilms and resistance genes contained in plasmids, integrons, and transposons. One hundred and thirty-three Salmonella isolates from different stages of the production line, such as feed manufacturing, hatchery, broiler farm, poultry farm, and slaughterhouse, were identified, serotyped and sequenced. The most predominant serotype was Salmonella Infantis. Phylogenetic analyses demonstrated that the diversity and spread of strains in the pipeline are serotype-independent, and that isolates belonging to the same serotype are very closely related genetically. On the other hand, Salmonella Infantis isolates carried the pESI IncFIB plasmid harboring a wide variety of resistance genes, all linked to mobile genetic elements, and among carriers of these plasmids, the antibiograms showed differences in resistance profiles and this linked to a variety in plasmid structure, similarly observed in the diversity of Salmonella Heidelberg isolates carrying the IncI1-Iα plasmid. Mobile genetic elements encoding resistance and virulence genes also contributed to the differences in gene content. Antibiotic resistance genotypes were matched closely by the resistance phenotypes, with high frequency of tetracycline, aminoglycosides, and cephalosporins resistance. In conclusion, the contamination in the poultry industry is described throughout the entire production line, with mobile genetic elements leading to multi-drug resistant bacteria, thus promoting survival when challenged with various antimicrobial compounds. Copyright © 2023 Krüger, Pardo-Esté, Zepeda, Olivares-Pacheco, Galleguillos, Suarez, Castro-Severyn, Alvarez-Thon, Tello, Valdes and Saavedra.
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    The Transcription Factor ArcA Modulates Salmonella’s Metabolism in Response to Neutrophil Hypochlorous Acid-Mediated Stress
    (Frontiers Media S.A., 2019-12) Pardo-Esté, Coral; Castro-Severyn, Juan; I. Krüger, Gabriel; Cabezas, Carolina Elizabeth; Briones, Alan Cristóbal; Aguirre, Camila; Morales, Naiyulin; Baquedano, Maria Soledad; Sulbaran, Yoelvis Noe; Hidalgo, Alejandro A.; Meneses, Claudio; Poblete-Castro, Ignacio; Castro-Nallar, Eduardo; Valvano, Miguel A.; Saavedra, Claudia P.
    Salmonella Typhimurium, a bacterial pathogen with high metabolic plasticity, can adapt to different environmental conditions; these traits enhance its virulence by enabling bacterial survival. Neutrophils play important roles in the innate immune response, including the production of microbicidal reactive oxygen species (ROS). In addition, the myeloperoxidase in neutrophils catalyzes the formation of hypochlorous acid (HOCl), a highly toxic molecule that reacts with essential biomolecules, causing oxidative damage including lipid peroxidation and protein carbonylation. The bacterial response regulator ArcA regulates adaptive responses to oxygen levels and influences the survival of Salmonella inside phagocytic cells. Here, we demonstrate by whole transcriptomic analyses that ArcA regulates genes related to various metabolic pathways, enabling bacterial survival during HOCl-stress in vitro. Also, inside neutrophils, ArcA controls the transcription of several metabolic pathways by downregulating the expression of genes related to fatty acid degradation, lysine degradation, and arginine, proline, pyruvate, and propanoate metabolism. ArcA also upregulates genes encoding components of the oxidative pathway. These results underscore the importance of ArcA in ATP generation inside the neutrophil phagosome and its participation in bacterial metabolic adaptations during HOCl stress. © Copyright © 2019 Pardo-Esté, Castro-Severyn, Krüger, Cabezas, Briones, Aguirre, Morales, Baquedano, Sulbaran, Hidalgo, Meneses, Poblete-Castro, Castro-Nallar, Valvano and Saavedra.